Polytrimethylene ether glycol and its uses have been described in the art. Preferred methods for preparation of polytrimethylene ether glycol involve acid catalyzed polycondensation of 1,3-propanediol. For example, U.S. Pat. No. 6,720,459, which is incorporated herein by reference, discloses a continuous process for preparation of polytrimethylene ether glycol from 1,3-propanediol using a polycondensation catalyst, preferably an acid catalyst.
WO99/01496, which is incorporated herein by reference, discloses a process for the purification of polyethers includes the steps of (a) heating a polyether glycol with water for a time and at temperature sufficient to substantially hydryrolyze esters formed during polymerization, (b) separating the polyether from the water, and (c) subjecting the polyether recovered from step (b) to further washing with hot water to remove residual acid.
US 2002-0007043 A1, which is incorporated herein by reference, describes a purification procedure for crude polytrimethylene ether glycol obtained from an acid catalyzed polymerization process comprising (1) a hydrolysis step to hydrolyze the acid esters formed during the acid catalyzed polymerization, (2) phase separation and water extraction steps to remove the soluble acid catalyst, generating an organic phase and a waste aqueous phase, (3) a base treatment of the organic phase to neutralize and precipitate the residual acid present, and (4) drying and filtration of the polymer to remove residual water and solids. It is clear from US 2002-0007043 A1 that when sulfuric acid is used as a catalyst to make polyether glycols from their corresponding diols, it is preferred to include a hydrolysis step because a substantial portion of the acid is converted to the ester, alkyl hydrogen sulfate. These ester groups act as emulsifying agents during the water washing process, thus causing the washing process to be difficult and time consuming, and causing incomplete acid removal. The hydrolysis step is also important in order to obtain polymer with the high dihydroxy functionality required to use the polymer as a reactive intermediate. When the hydrolysis step is incorporated into the process, it is generally found that the phase separation between the water and polytrimethylene ether glycol phases can take a substantial amount of time, e.g. up to about 35–40 hours. Consequently, there is a need for a method to reduce the phase separation time.
JP2004-182974A, which is incorporated herein by reference, discloses a polycondensation process for preparing polyether polyols, including preparing polytrimethylene ether glycol from 1,3-propanediol, utilizing a polycondensation catalyst system that contains both an acid and a base. It is disclosed that the use of this catalyst system produces polyether polyol with high degree of polymerization and low color under mild conditions. The purification process utilizes a hydrolysis step wherein water and organic solvent that has affinity for both water and the polyether polyol are used and subsequent separation into aqueous and organic phases. In one example this patent application discloses use of calcium hydroxide to treat the organic phase after the phase separation. This process has a disadvantage in that organic solvent ends up in both the aqueous and polymer (polyether polyol) phases. It is undesirable to have a solvent present in the aqueous phase because the disclosed organic solvents are flammable and, thus, it is necessary to recover the organic solvent from the aqueous phase prior to reuse or disposal of the water and in order to reuse the organic solvent. In addition, the presence of solvent in the aqueous phase may dissolve more polymer or oligomers and therefore the polymer yields will be lower. Consequently, a process that does not result in solvent and polyether polyol in the aqueous phase is desired. This process also has the disadvantage that the resulting polyether polyols contain base catalyst residues.